FI82503C - Method and apparatus for reducing the amount of leakage air and the addition of the web in drying drawers and covers - Google Patents

Description

82503

Method and apparatus for reducing air leakage in dryer boxes or hoods and for reducing flutter on the track Förfarande och anordning för att minska pä läckageluftmängderna 5 och fladdrandet av faan i torkningslädor eller -käpor

The invention relates to a method for reducing the amount of leakage air in dryer boxes or hoods and for reducing the flutter of the track in connection with said boxes or hood inlets and / or outlets, in which the track to be dried and possibly otherwise treated is led through the inlet to the box or hood. through the outlet so that the moving track does not touch the fixed parts 15 connected to the openings.

The invention further relates to an apparatus for carrying out the method of the invention, comprising a dryer box, such as a hover box or a hood of a drying section, having an inlet opening of a box to be dried inside said box or hood and a corresponding outlet extending transversely over the entire width of the web.

The hoods or various dryer boxes of the drying section of the paper machine comprise an inlet opening of the web to be dried, which is usually in the front wall of the hood or box, and an outlet opening, respectively, which is usually in the back wall of the hood or dryer box. Said openings have had to be dimensioned quite high, in particular due to the flutter of the web, with the consequent disadvantage that the amounts of leakage air become harmfully large. Harmful flutter occurs in the web in connection with said openings 30 in previously known dryers, which may cause the web to break, resulting in downtime.

The state of the art and its drawbacks related to the invention will be described in more detail later in the part of the application referring to the drawings.

The object of the present invention is to provide a new method and a device by which the above-mentioned drawbacks can be avoided. In order to achieve the above and later objects, the method of the invention is mainly characterized in that the track travel is stabilized by congesting the track with both the inlet and outlet. a layer of air carried between said openings between the track and the guide vane arranged below it, in which areas a relatively thin air cushion is thus formed.

The device according to the invention, in turn, is mainly characterized in that lower track guide vanes are arranged in connection with both the inlet opening and the outlet opening so as to stabilize the passage of the track in connection with the vanes at a small distance from the wing bearing surface.

According to the invention, lower track guide vanes are placed in both track openings of the hood of the fluidized box, the corresponding other dryer box or the drying section 15 so that they are substantially in the track line or a few millimeters above or below it. The wings fit best on the base paper side of the track. The layer of air carried by the track constricts between the track and the wing and causes an air cushion 0.5-4 mm, usually suitable for about 1 ... 2 mm thick, between them. As a result, the course of the track is stable and the amount of leakage air between the track and the wings is very small. Due to less flutter, without the risk of contact, the upper edge of the track opening can also be lowered, which reduces the amount of leaking air on this side as well.

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Based on the test results, it can be considered a realistic estimate that due to the invention the leakage air volumes are reduced by about half compared to those obtained with known arrangements. In practice, lower energy consumption, better driveability and better air dry space are also significant advantages.

In the following, the closest prior art to the invention, its most obvious drawbacks, and some preferred application examples of the present invention will now be described in detail with reference to the accompanying drawings, in which:

Figure B shows graphically the amount of air flowing into the dryer box through the inlet as a function of web speed at different pressure levels inside the dryer box and at two previously known typical heights of different web openings.

Fig. C shows the amount of air flowing out of the dryer hose through the outlet opening as a function of the web speed in a manner similar to Fig. B.

Figure 1 schematically shows a previously known fluidized bed dryer in which the method and device according to the invention can be advantageously applied.

15

Figure 2 shows a web inlet and outlet provided with a guide vane according to the invention.

Figure 3 shows a first embodiment of a guide vane according to the invention in vertical section.

Figure 4 shows a second embodiment of a guide vane according to the invention in vertical cross-section.

Figure 5 shows a third embodiment of a guide vane according to the invention in vertical cross-section.

Fig. 6 shows a fourth embodiment of the control vane according to the invention as a vertical view.

30

Fig. 7 shows a fifth embodiment of a guide vane according to the invention in a vertical cross-section.

As is known, fluidized bed dryers or paper machine hoods are provided with track openings 14 and 15 or the like according to Figure A. The height K of the openings 14,15 is generally in the range of 30 to 60 mm and typically in the range of 30 to 45 mm. The aim is to keep the floating box 10 slightly pressurized. From the inlet 14 of the web W, leakage air flows into the hover box 10 in the direction of the arrows F1, because the path W carries with it without a boundary layer. Correspondingly, in the outlet opening 15, the circulating air of the fluid flows out of it in the direction of the arrows F. Due to the flutter of the web W, the track openings out 5 14,15 must be made high enough (K). The air flow in the track openings o 14.15 increases the flutter of the web W. The air coming out of the hover is humid and hot, which worsens the climate in the data center and increases the need for ventilation.

Figures B and C show the inflow and outflow air volumes measured by the test device in the track openings 14 and 15 of the fluidized box 10 according to Figure A. It can be seen from Figures B and C that the leakage air volumes increase approximately linearly with the track speed.

15 Figures B and C show the leakage air volumes at two different track opening heights, namely K = 30 mm and K = 45 mm. It can be seen from the figures that increasing the orifice from 30 mm to 45 mm significantly increases the amount of leakage air entering the fluidized bed 10, while said change in the height of the orifice K has very little effect on the amount of leakage air coming out. The effect of the pressure level P of the floating box on the amounts of leaking air is also clear from Figures B and C, in which two pressure levels of the interior 10 of the floating box P = 0 Pa and P = -10 Pa have been used.

Large amounts of leaking air cause a number of problems. In order to keep the fluid 25 under pressure, the amount of exhaust air must be kept high, so that the humidities of the exhaust air are low (normally at the level of 30 ... 70 g / kg / kg). As a result, energy consumption is also high (efficiencies are normally at the level of 40 ... 50%).

The fluidized bed dryer shown in Fig. 1 comprises a fluidized box 10 consisting of a front wall 11, a rear wall 12 and upper and lower walls 13 and end walls. Inside the floating box 10 there are two opposite nozzle units 25a resp. 25b, with bearing surfaces 26a resp. 26b limit the air drying support space resp. web W on both sides-35 Iin. From the nozzle trawl 27 of the bearing surfaces 26a, 26b, which are shown only diagrammatically in Fig. 1, blows F1 are derived, which dry and at the same time non-contact support the web W as it passes between

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5 82503 1 and through. As the nozzles 27, overpressure or underpressure nozzles known per se can be used, the details of the construction of which are referred to in the applicant's FT patents Nos. 68723 and 60261 (respectively U.S. Pat. Nos. 4,247,993 and 4,384,666). The fluidized bed box 10 has an inlet-5 opening 14 and an outlet opening 15 of the web W.

An air circulation system of a fluidized bed shown schematically in Fig. 1 is described below, comprising an supply air duct 32 and a return air duct 36. The supply air duct 32 opens through the dampers 33a and 10 . The blowers F1 are collected in a fluidized box 10, from which the return air sucked by the fan 30 is taken through the connections 35 and the control dampers 35a to the return air duct 36. The replacement air is taken in via a duct 31 provided with a control damper 31a if necessary. The exhaust air is sucked in by the exhaust air fan 38 through a duct 34, which is provided with a control damper 34a, if necessary. Figure 1 of the fan 30 in accordance with the discharge channel is connected to the gas burner 37, wherein the air is heated to a suitable lämpötllatasoon before it is passed lei-20 jukuivaimen supply air duct 32.

Figure 2 shows a preferred wing arrangement according to the invention. Accordingly, in connection with the web inlet 14, there is a planar guide vane 20 having a planar front portion 21 inclined upwardly in the direction of travel of the web, the height 21 of which is denoted by K1, the length Lei and the length L1 of the planar bearing surface 23. According to Fig. 2, in connection with the outlet 15 of the web W, the rear wall of the floating box 10 has a planar guide wing 20 below the web W with an upwardly sloping front 21 and a corresponding lower sloping rear 22 in the direction of travel of the web W. The slopes 21 and 22 are 11a, and the length of the planar bearing portion 23 of the web W by L.

Figures 3-7 show some preferred vertical cross-sections of the guide vanes of the inlet 14 and the outlet 35, mainly in the order of preference. In Fig. 3-7, the arrow A indicates the direction of travel of the web W. According to Fig. 3, the wing 20 has at an angle / 3 an upper chamfer 6 82503 Ί a front portion 21a and then a portion having a radius of curvature R, followed by a planar bearing surface portion 23 terminating in a rounded edge portion 22a. Typical dimensions of the wing in Figure 3 are 5 R 20 ... 60 mm (b 20 ... 45 ° 30 ... 60 mm L, 50 ... 100 mm 10 In Figure 4, the wing has a straight upward sloping front 21b at an angle / *> to a planar bearing surface portion terminating in a rounded fold portion 22b on the trailing side of the track Typical dimensions of the wing of Figure 4 are 15/3 20 ... 45 °

Lj 30 ... 60 mm I'2 50 ... 100 mm

Figure 5 shows a quarter-circular front portion 21c having a radius of curvature R, the tangential extension of which is a planar bearing surface portion 20 terminating in a rounded fold 22c. Typical dimensions in Figure 5 are R 50 ... 100 mm 25 30 ... 60 mm 50.. . 100 mm

In Fig. 6, both edges of the planar bearing surface 20 have folds 21d and 22d having the same or different radii of curvature R, which tan-30 are genially connected to the planar bearing surface 20. Typical dimensions of Fig. 6 are R 10 ... 20 mm 60 .. 120 mm

Fig. 7 shows a wing, significantly different from the above, consisting of a semicircular slider portion 20R, the wrapper of which

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7 82503 The radius R is typically in the range R * 40 ... 80 mm. Corresponding wings, e.g. in the form of a part of an ellipse, such as a half-ellipse, can also be used.

5 It is typical of the guide vane examples described above that they are located below the path W passing them, stabilizing its travel. This stabilizing effect is based on the fact that the moving track W always carries without it a boundary layer, which constricts between the track W and the bearing surface 23 of the wing 20. This usually results in approx.

10 1 ... 2 mm thick Air cushion between track W and wing support Lille. This air cushion stabilizes the passage of the track W quite close to the wing carrying surface 23. Therefore, only a very small amount of air can pass between the track W and the bearing surface 23.

Since the wing arrangement according to the invention with its bearing surfaces stabilizes the track W so that its flutter amplitude is very small, the upper edge of the track opening 14,15 can also be lowered even lower. Thus, the amount of leakage air coming above the track W can also be substantially reduced.

20

The track control vanes 20 shown in Figure 2 were tested in a test rig. In Experiment 1 the inlet vane 20 was 10 mm and the outlet vane 15 was 5 mm below the track line, in Experiment 2 both wings were in the track line, in Experiment 3 they were 5 mm above the track line 25 and in Experiment 4 they were run without wings (previously known track openings). The speed of the track was 1250 m / min in all situations.

According to the test results, the wings 20 are most preferably kept in or slightly above the line. By means of the vanes 20, the amount of fluid leakage air 30 can be reduced by about half, because no leakage air enters significantly between the track W and the vanes 20, and due to less flutter, the height of the opening above the track W can also be narrower.

35 Test 1. a = 10 mm, b = 5 mm, c = 30 mm, d = 25 mm

The trajectory of the track was stable in both track openings 14 and 15. The vanes 20 did not bend the trajectory W from its centerline and the distance of the 8 82503 1 track W from the vanes 20 remained constant.

Experiment 2. a = 0 mm, b = 0 mm, c = 20 mm, d = 20 mm

The course of track W was stable. In the inlet IA, the distance of the track from the 5 wings was tight 0 ... 2 mm, loose 0 ... 2.5 mm.

At exit 15, track W was very close to the wing.

The vacuum of 25 Pa in box 10 had no effect on the path W.

Experiment 3. a = -5 mm, b = -5 mm, c = 12 mm, d = 12 mm 10 The course of the track was completely stable. The distance from the wing 20 in both openings is 14.15 0 ... 1 mm.

The vacuum of 20 Pa in box 10 had no effect on the course of the track.

Experiment 4. Without guide vanes (cf. Fig. A), heights Kq = 40 mm of track openings 14,15 15, outlet 45 mm. The path W fluttered in the outlet 14 with an amplitude of 5 ... 10 mm, in the outlet 15 less. At a box vacuum of 10 Pa, the flutter was stronger than at zero pressure.

Although the invention has been described above with reference to applications in which the path of the web is horizontal, it will be appreciated that the invention may also be used in fluidized bed or hood applications where the web path is up or down.

25 The web passage through the dryer is not always planar and the direction of entry of the web may differ from its direction of departure. In this case, different guide vanes can be used in the inlet opening and in the outlet opening, which can still be on different sides of the web.

In the following, the claims are defined, within the scope of which the inventive idea is defined, the various details of the invention may vary within the scope of the inventive idea defined by the following claims.

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Claims (11)

A method of reducing the leakage amount of air and the flaking of the web (W) in dryer cloths (10) or jaws in connection with the entrance openings (14) and / or the outlet openings (15) of said leather (10) or jaws; by which method the web (W) is to be dried and possibly otherwise treated is guided through the entrance opening (14) inside the leather (10) or hood, from which it is removed via an exit opening (15) in such a way that the moving web ( W) does not touch the fixed parts in connection with the openings (14, 15), characterized in that the bed in connection with the entrance opening (14) and the exit opening (15) stabilizes the web (W) race by penetrating the air layer. which is conveyed with the web (W) between a guide rudder (20) arranged below the web (W) in connection with said openings (14,15) in which areas a relatively thin air cushion is thereby formed. 2. A method according to claim 1, characterized in that a method of control rod (20) which stabilizes the web (W) race (20) is used in the process to stabilize the web (W) on a 0.5. .4 mm, most preferably about 1 ... 2 mm, distance from the bearing surface (23) of the rudder (20). Method according to claim 1 or 2, characterized in that said guide rods (20) with their supporting surfaces (23) are placed on the side of the base paper. Method according to any of claims 1-3, characterized in that the plane of the guide rudder (23) is arranged substantially in the web line or some millimeter above or below the web line. 30 5. A method according to any one of claims 1-4, characterized in that the guide rudder (20) is used in connection with such a float (10) or jaw in a drying portion, within which substantially a pressure corresponding to the outer atmosphere or 35 to this low suppression of class 5 ... 50 Pa. i2 82503 Apparatus intended to carry out the method according to any one of claims 1-5, which comprises a drying cloth, such as a sulfur (10) older a cutter in the drying portion, there being an entrance opening (14) and a corresponding exit opening (15) for the web ( W) which is to be guided to be dried within g of said ladle (10) or clamped, which opening in the transverse direction extends along the entire width of the web, characterized in that in connection with both the entrance opening (14) and the exit opening (15) there is arranged a below rudder (20) to guide the web so that they stabilize the course 1 of the web (W) with the rudder (20) at a small distance from the bearing surface (23) of the rudder (20). Device according to claim 6, characterized in that the support surface (23) of the web guide rudder (20) is located substantially in the web line or a few millimeters above or below it. 15 Device according to claim 6 or 7, characterized in that in the rudder (20) for controlling the web there is in the running direction (A) of the web (W) an oblique front part (21a, 21b, 21c) towards the web line which is planar (Figs. 3,4) or curved (Figs. 5, 6, 7), and the said front portion joins a substantially planar portion (23) of the support surface by mediating an edge or tangential rounding (Figure 4), which portion of the support surface ends directly at the edge or at the rounded rear edge portion (22a, 22b, 22c, 22d). Device according to claim 8, characterized in that the angle between said front part (21a, 21b, 21c) and the web plane is = 20 ... 45 °, that the length of said front part (21a, 21b, 21c) in the running direction of the web is = 30 ... 60 mm and the length of said planar portion (23) of the carrier surface in the running direction of the web (W) = 50 ... 100 mm. 30 10. Apparatus according to claim 6, characterized in that the shape of the cross-sectional shape of the guide rod is continuously curved, such as a semicircle (Figure 7), corresponding to a half-ellipse or other suitable continuous curved line. 35 i3 82503 Device according to any of claims 6-10, characterized in that the total height of the web opening (14,15) from the support surface (23) of the guide tube (20) towards the fixed part (c, d) is within the range 10.. .40 mm, most preferably 12 ... 30 mm. 5 10 15 20 25 30 35